Are you interested in such a utility?
I derived this utility from TextApp, that comes with the JasperReports sample applications.
It uses command line arguments in order to assign values to $P{…} within JRXML resp. .jasper.
The advantage over installing JasperReports as a server: it makes use of JasperReports’ libraries, but it’s stand-alone and pretty lightweight.
Update 2011-04-20
My next “major” feature enhancement for this utility: Let it make use of XML elements and their attributes resp. “content” instead of command line arguments. That should deal with UTF-8 text much better than command line arguments to be supplied from within shell scripts. Actually the JasperReports toolkit already knows how to work with XML, but my point is to make the usage of XML supplied fields look almost like $P{…}.
(Nota bene: this was written rather in a hurry and may need some rephrasing. Once I will start the implementation, I will certainly do this.)